1. Field of the Invention
The present invention relates to footwear and the manufacture of footwear. The invention concerns, more particularly, a footwear upper formed through a textile manufacturing process to have areas with different physical properties.
2. Description of Background Art
Conventional articles of athletic footwear generally include two primary elements, an upper and a sole structure. The upper is attached to the sole structure and forms a void on the interior of the footwear for securely and comfortably receiving a foot. The sole structure attenuates ground reaction forces and absorbs energy as the footwear contacts the ground, and often incorporates multiple layers that are conventionally referred to as a midsole and an outsole. The midsole forms the middle layer of the sole and serves a variety of purposes that include controlling potentially harmful foot motions, such as over pronation; shielding the foot from excessive ground reaction forces; and beneficially utilizing such ground reaction forces for more efficient toe-off. The outsole forms the ground-contacting element of footwear and is usually fashioned from a durable, wear resistant material that includes texturing to improve traction. The sole structure may also include an insole, which is a thin, cushioning member located within the upper and adjacent to a sole of the foot to enhance footwear comfort.
The upper of most conventional articles of footwear is generally formed from multiple material elements that are stitched and adhesively bonded together to form a comfortable structure for receiving the foot. Conventional athletic footwear may include, for example, an exterior formed of leather and polymer textile materials that are resistant to abrasion and provide the footwear with a particular aesthetic. Foam materials may be located on the interior of the upper to enhance the comfort of the upper, and moisture-wicking textiles may be positioned adjacent the foot to limit the perspiration within the upper.
In a departure from the conventional upper described above, NIKE, Inc. of Beaverton, Oreg., United States manufactures athletic footwear with a knit upper under the PRESTO trademark. The knit upper includes a plurality of material elements that are formed through a knitting process. In manufacturing the upper, the material elements are cut from a larger element and sewn together along their respective edges to form a generally hollow structure for receiving a foot. The upper, therefore, includes a plurality of separately-formed, knit sections stitched together to form seams between the various sections.
Based upon the discussion above, the uppers for athletic footwear are generally constructed of numerous materials or elements. In manufacturing the uppers, considerable time and labor is expended in cutting the various elements to have a proper shape and size, and stitching or adhesively bonding the elements to each other. Consequently, these footwear manufacturing techniques are not only time and labor intensive, but also result in an undesirable amount of waste materials resulting from the trimming of the materials to make the elements.
A unitary upper formed through a knitting process is disclosed in U.S. Pat. No. 2,147,197 to Glidden. The upper is knitted to have a sock-like structure in which areas subjected to greater wear and in which a lower degree of elasticity is desired are more densely fabricated to provide heavier weight and less extensibility than in other portions. This may be accomplished, for example, by changing the type of stitch. Other areas, such as the ankle portion, may be formed to have a ribbed construction to provide softness and elasticity.